ACPI/IORT: Remove direct access of dev->iommu_fwspec

Use the accessor functions instead of directly dereferencing
dev->iommu_fwspec.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20200326150841.10083-3-joro@8bytes.org

drivers/acpi/arm64/iort.c

@@ -1015,6 +1015,7 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
 		return ops;
 
 	if (dev_is_pci(dev)) {
+		struct iommu_fwspec *fwspec;
 		struct pci_bus *bus = to_pci_dev(dev)->bus;
 		struct iort_pci_alias_info info = { .dev = dev };
 
@@ -1027,8 +1028,9 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
 		err = pci_for_each_dma_alias(to_pci_dev(dev),
 					     iort_pci_iommu_init, &info);
 
-		if (!err && iort_pci_rc_supports_ats(node))
-			dev->iommu_fwspec->flags |= IOMMU_FWSPEC_PCI_RC_ATS;
+		fwspec = dev_iommu_fwspec_get(dev);
+		if (fwspec && iort_pci_rc_supports_ats(node))
+			fwspec->flags |= IOMMU_FWSPEC_PCI_RC_ATS;
 	} else {
 		int i = 0;